Before Vaccines, Diphtheria Used to Kill Hundreds Each Year. Now It’s Back in Australia

Why It Matters

The diphtheria flare‑up underscores how gaps in vaccine coverage can quickly revive a once‑controlled disease, threatening public health and straining limited treatment resources. It signals urgent need for targeted immunisation campaigns and reinforced supply chains for life‑saving antitoxin.

Key Takeaways

• NT reports 17 respiratory diphtheria cases in past month
• WA Kimberley region sees 27 diphtheria cases, 25% respiratory
• Childhood vaccine coverage fell to 90.5% for 12‑month olds in 2025
• Only 91.9% of NT five‑year‑olds fully vaccinated, lowest nationally
• Diphtheria antitoxin stockpiles are limited, complicating treatment

Pulse Analysis

The current diphtheria outbreaks in Australia’s Northern Territory and Western Australia represent a stark reversal of a disease that was virtually eliminated after the introduction of the DTP vaccine in the 1930s. In the past month alone, the NT has confirmed 17 respiratory cases, while the Kimberley region of WA has recorded 27 infections, a quarter of which affect the airway. These numbers, though modest compared with historic mortality, are alarming because they signal the re‑emergence of a toxin‑producing bacterium in communities with waning herd immunity. The disease’s dual presentation—respiratory, which can cause fatal airway obstruction, and cutaneous, which serves as a reservoir for transmission—complicates containment efforts, especially in remote areas where healthcare access is limited.

A key driver of the resurgence is the decline in routine childhood immunisation rates. National coverage for the three‑dose DTP series dropped from 94.8% in 2020 to 90.5% among 12‑month‑olds by 2025, the lowest level in five years. In the NT, only 91.9% of five‑year‑olds have completed the schedule, the lowest among Australian jurisdictions, while Indigenous children in the region maintain slightly higher rates. The dip in coverage reflects practical barriers—travel distance, appointment availability—and growing vaccine hesitancy fueled by mistrust of health messaging post‑COVID. These gaps create pockets of susceptibility where the bacterium can circulate unchecked, turning a preventable infection into a public‑health emergency.

Addressing the outbreak requires a multi‑pronged approach. Immediate actions include targeted catch‑up vaccination drives in affected regions, leveraging schools, community health centres, and Aboriginal medical services to reach under‑immunised children and adults. Simultaneously, governments must secure and expand antitoxin stockpiles, as current supplies are insufficient for a larger wave of severe cases. Long‑term solutions involve investing in primary‑care infrastructure to enable longer, reimbursed vaccine‑consultations, and deploying culturally competent communication strategies to rebuild confidence. By restoring high immunisation coverage and ensuring treatment readiness, Australia can prevent diphtheria from re‑establishing a foothold and protect vulnerable populations from this once‑forgotten threat.